Great strides have been made in recent years in the field of oral health care. However, much remains to be done. While the development of anticaries agents, especially the fluorides, has led to a decline in the incidence of tooth caries it is desirable to even further decrease the number of teeth affected thereby. Moreover, attention in the oral health care field has increasingly focused on the problems of gum disease, periodontitis. While antibacterial agents have been proposed of inclusion in products for use by consumers in the treatment of periodontitis, certain problems have been associated with their use. For example, use of chlorhexidine, which has been known as as antibacterial agent, has been associated with staining problems; it produces yellow to dark brown stains on teeth, tongue and oral mucosa. Furthermore, chlorhexidine has a very bitter taste.
There has been a need, therefore, for developing a dentifrice formulation including chlorhexidine or other antimicrobial agents such as quaternary ammonium antibacterial compounds, which does not cause staining of the teeth and which has an improved taste. Moreover, dentifrices having improved anticavity effects are also desirable.
Staining can be troublesome, whether or not chlorhexidine is the cause. The accumulation of stains on tooth surfaces poses an esthetic problem for many individuals.
Plaque is a common factor in caries, gum disease and staining and greatly contributes to their development. Proper oral hygiene as currently practiced requires that plaque be removed or prevented not only for cosmetic purposes but also to eliminate a source of potential injury to teeth and gums.
Silicones have previously been suggested for inclusion in dentifrice compositions in that it has been proposed that they would coat the teeth and thereby prevent cavities and staining. For example, British Patent Specification 689,679 discloses a mouthwash containing an organopolysiloxane for the purpose of preventing adhesion of, or for removal of, tars, stains, tartar and food particles from the teeth. However, polymers such as those disclosed in the '679 specification, have not generally been successfully used for coating the teeth since it has been found that the polysiloxane does not adhere to the teeth for prolonged periods of time. Therefore, the need for dentifrice formulations including a hydrophobic substance which effectively coats the teeth has not been satisfied.
Viccaro, et al. copending application S/N 07/276,704 field Nov. 28, 1988 and entitled "Dentifrices Containing Aminoalkyl Silicones" discloses dentifrice formulations including aminoalkylsilicones for coating the teeth and inhibiting stain and caries. The aminoalkylsilicones have been found to be more substantive than alkylsilicones, apparently due to the interaction of the positively charged nitrogen of the amine with the negative charges on the surface of the teeth. However, amine groups tend to react with certain chemical groups found in toothpaste components such as the aldehydes of flavoring ingredients. Consequently, aminoalkylsilicones bearing amine groups capable of being protonated over a broad pH range yet of reduced reactivity are desirable.
Silicones have been used or proposed for use in many consumer products other than dentifrices. Where silicones are included to coat charged objects, such as furs, aminoalkylsilicones will be of use. Like dentifrices, these products may contain compounds having moieties which tend to react undesirably with amine groups. Therefore, aminoalkylsilicones in which the amine group is somewhat deactivated would be useful in these applications, as well.
Attempts have been made to modify the structure of aminosilicones to decrease the reactivity of the amino groups. In U.S. Pat. No. 4,507,455 aminosilicones are reacted with acetic anhydride to form amides. It is believed that the modifications seriously limit the pH range over which the amines will be protonated thereby detracting from the usefulness of the respective aminoalkylsilicones in applications, such as those mentioned above, wherein protonation of the amine is important. Also, U.S. Pat. No. 4,472,566 discloses the reaction of aminosilicones with benzylchloride to yield secondary and tertiary amines.
Morehouse U.S. Pat. No. 3,032,577 discloses organosiloxanes which are said to be useful for a variety of applications in the synthetic polymer art, particularly as flocculating agents for aqueous dispersion of clay. The organosiloxanes of the Morehouse patent include units of the formula: ##STR1## wherein --OZ--is the divalent group derived from a monoepoxide by opening of the oxirane ring, HO is interconnected to N through 2 carbon atoms, a is an integer from 0 to 1, n is an integer from 3 to 15, and R may be hydrogen, monovalent hydrocarbon or --C.sub.n H.sub.2n (R.sup.1 b)SiO.sub.(3.sub.2 .sub.-b).; Morehouse does not appear to suggest that his compounds would be useful in dentifrices and the like, nor does he seem to recognize the desirability of using compounds which can yield a higher positive charge density.